Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic process, a process cartridge, and an apparatus main body for an image forming apparatus.
Description of the Related Art
A conventional process cartridge is known in which a photosensitive drum and a process means for forming a developer image on the photosensitive drum are integrated as a cartridge. The process cartridge can be attached to and detached from the apparatus main body of an image forming apparatus. The cartridge system enables the user to maintain the image forming apparatus by himself, without a servicemen.
When an electrostatic latent image is developed on a photosensitive drum, a contact development system is sometimes used in which developer is supplied to the photosensitive drum by bringing a development roller into contact with the photosensitive drum. In the contact development system, since the development roller and the photosensitive drum need to be brought into contact with each other, the development roller is biased with respect to the photosensitive drum.
However, where the state of contact of the development roller with the photosensitive drum is maintained for a long time, the development roller can be deformed, or a toner interposed between the development roller and the photosensitive drum can be damaged. As a result, image defects can occur. For this reason, the feature of separating the development roller and photosensitive drum from each other when no image is formed is widely used in process cartridges.
For example, a configuration has been suggested in which a process cartridge is mounted in the rotation axis direction of a photosensitive drum from an insertion port provided in an apparatus main body (Japanese Patent Application Publication No. 2008-9295 (JP 2008-9295 A)). In this invention, the development roller is withdrawn from the photosensitive drum in conjunction with the operation of pulling out the process cartridge from the apparatus main body. Further, the development roller is brought into contact with the photosensitive drum in conjunction with the operation of inserting the process cartridge into the apparatus main body of the image forming apparatus.
Further, an image forming apparatus has been suggested which is provided with a door for opening and closing the insert ion port for inserting a process cartridge into the apparatus main body, and by closing the door after the process cartridge has been inserted into the apparatus main body, the development roller and photosensitive drum are brought into contact or separated in conjunction with the operation of closing the door (JP 2005-49525 A).
However, in the invention disclosed in JP 2008-9295 A, the separated development roller is brought close to the photosensitive drum in the course of inserting the process cartridge into the insertion port. Therefore, the insertion port of the apparatus main body needs to have a shape that allows to pass therethrough both the process cartridge in a state in which the development roller and photosensitive drum are brought close to each other and the process cartridge in a state in which the development roller and photosensitive drum are separated from each other.
In this case, a clearance is present between the process cartridge and insertion port when the process cartridge passes through the insertion port. As a result, the process cartridge can be inserted into the insertion port in a wrong mounting posture, or the posture of the process cartridge can be unstable during the attachment/detachment operation of the process cartridge. As a result, the important components, such as the photosensitive drum, can come into contact with the apparatus main body and these important components can be damaged.
Meanwhile, in the invention disclosed in JP 2005-49525 A, a part is needed for bringing the development roller and photosensitive drum into contact with each other or separating them from each other in conjunction with the operation of closing the door. Therefore, the number of parts used in the image forming apparatus is increased, and the production cost of the image forming apparatus rises.